Imaging Device

ABSTRACT

A device for capturing images where the incident light passes through a modulator that adjusts to provide a selected image. Imagewise light is received in a sensor which is in communication with a processor that implements an optimization algorithm. The processor is in communication with the modulator and controls functioning of the modulator to optimize and to obtain the selected image.

RELATED APPLICATION

This application is a Divisional of U.S. patent application Ser. No.10/696,046, filed on Oct. 29, 2003, which is a Continuation-In-Part ofU.S. patent application Ser. No. 10/011,187, filed on Nov. 13, 2001 nowU.S. Pat. No. 6,648,473 entitled HIGH-RESOLUTION RETINA IMAGING AND EYEABERRATION DIAGNOSTICS USING STOCHASTIC PARALLEL PERTURBATION GRADIENTDESCENT OPTIMIZATION ADAPTIVE OPTICS, the entire disclosures of whichare incorporated by reference herein in their entireties.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to a method and a system for high-resolutionretinal imaging, eye aberration compensation, and diagnostics based onadaptive optics with direct optimization of an image quality metricusing a stochastic parallel perturbative gradient descent technique.

Adaptive optics is a promising technique for both diagnostics of opticalaberrations of the eye and substantially aberration-free high-resolutionimaging of the retina. In existing adaptive optics techniques adaptivecorrection is based on illumination of the retina by a collimated laserbeam to create a small size laser location on the retina surface withconsequent measurement of phase aberrations of the wave scattered by theretina tissue. Correction of eye optical aberrations is then performedusing the conventional phase conjugation technique.

This traditional approach has several important drawbacks. One importantdrawback is the danger due to an invasive use of the laser beam focusedonto the retina. Other drawbacks include overall system complexity andthe high cost of the necessary adaptive optics elements such as awavefront sensor and wavefront reconstruction hardware. Moreimportantly, due to aberrations the laser beam location size on theretina is not small enough to use it as a reference point-type lightsource and hence conjugation of the measured wavefront does not resultin optimal optical aberration correction. Additionally, the traditionalapproach can produce a turbid image that can make performing anoperation with a microscope difficult.

One prior art method using a laser is taught in U.S. Pat. No. 6,095,651entitled “Method and Apparatus for Improving Vision and the Resolutionof Retinal Images”, issued to Williams, et al. on Aug. 1, 2000. InWilliams, et al. teaches a method and apparatus for improving resolutionof retinal images. In this method, a point source of light is producedon the retina by a laser beam. The source is reflected from the retinaand received at a lenslet array of a Hartman-Shack wavefront sensor.Thus, higher order aberrations of the eye can be measured and data canbe obtained for compensating the aberrations using a system including alaser. U.S. Pat. Nos. 5,777,719 and 5,949,521 provide essentially thesame teachings. While these references teach satisfactory methods forcompensating aberrations, there is some small risk of damaging theretina since these methods require applying laser beams to the retina.

U.S. Pat. No. 5,912,731, entitled “Hartmann-type Optical WavefrontSensor” issued to DeLong, et al. on Jun. 5, 1999 teaches an adaptiveoptics system using adjustable optical elements to compensate foraberrations in an optical beam. The aberrations may be caused, forexample, by propagation of the beam through the atmosphere. Theaberrated beam can be reflected from a deformable mirror having manysmall elements, each having an associated separate actuator.

Part of the reflected beam taught by DeLong can be split off anddirected to impinge on a sensor array which provides measurementsindicative of the wavefront distortion in the reflected beam. Thewavefront distortion measurements can then be fed back to the deformablemirror to provide continuous corrections by appropriately moving themirror elements. Configurations such as this, wherein the array of smalllenses as referred to as a lenslet array, can be referred to asShack-Hartmann wavefront sensors.

Additionally, DeLong teaches a wavefront sensor for use in measuringlocal phase tilt in two dimensions over an optical beam cross section,using only one lenslet arrangement and one camera sensor array. Themeasurements of DeLong are made with respect to first and secondorthogonal sets of grid lines intersecting at points of interestcorresponding to positions of optical device actuators. While thismethod does teach the way to correct aberrations in a non-laser lightsystem, it cannot be used in cases where lasers are required.

U.S. Pat. No. 6,007,204 issued to Fahrenkrug, et al. entitled “CompactOcular Measuring System”, issued on Dec. 28, 1999, teaches a method fordetermining refractive aberrations of the eye. In the system taught byFahrenkrug, et al. a beam of light is focused at the back of the eye ofthe patient so that a return light path from the eye impinges upon asensor having a light detecting surface. A micro optics array isdisposed between the sensor and the eye along the light path. Thelenslets of the micro optics array focus incremental portions of theoutgoing wavefront onto the light detecting surface so that thedeviations and the positions of the focused portions can be measured. Apair of conjugate lenses having differing focal lengths is also disposedalong the light path between the eye and the micro optics array.

U.S. Pat. No. 6,019,472, issued to Koester, et al. entitled “ContactLens Element For Examination or Treatment of Ocular Tissues” issued onFeb. 1, 2000 teaches a multi-layered contact lens element including aplurality of lens elements wherein a first lens element has a recesscapable of holding a volume of liquid against a cornea of the eye. Amicroscope is connected to the contact lens element to assist in theexamination or treatment of ocular tissues.

U.S. Pat. No. 6,086,204, issued to Magnante entitled “Methods andDevices To Design and Fabricate Surfaces on Contact Lenses and OnCorneal Tissue That Correct the Eyes Optical Aberrations” on Jul. 11,2000. Magnante teaches a method for measuring the optical aberrations ofan eye either with or without a contact lens in place on the cornea. Amathematical analysis is performed on the optical aberrations of the eyeto design a modified shape for the original contact lens or cornea thatwill correct the optical aberrations. An aberration correcting surfaceis fabricated on the contact lense by a process that includes laserablation and thermal molding. The source of light can be coherent orincoherent.

U.S. Pat. No. 6,143,011, issued to Hood, et al. entitled “HydrokeratomeFor Refractive Surgery” issued on Nov. 7, 2000 teaches a highspeedliquid jet for forming an ophthalmic incisions. The Hood, et al. systemis adapted for high precision positioning of the jet carrier. An airwaybeam may be provided by a collimated LED or laser diode. The laser beamcan be used to align the system.

U.S. Pat. No. 6,155,684, issued to Billie, et al. entitled “Method andApparatus for Precompensating The Refractive Properties of the Human EyeWith Adaptive Optical Feedback Control” issued on Dec. 5, 2000. Billie,et al. teaches a system for directing a beam of light through the eyeand reflecting the light from the retina. A lenslet array is used toobtain a digitized acuity map from the reflected light for generating asignal that programs an active mirror. In accordance with the signal theoptical paths of individuals beams in and the beam of light are made toappear to be substantially equal to each other. Thus, the incoming beamcan be precompensated to allow for the refractive aberrations of theeyes that are evidenced by the acuity map.

Additional methods for using adaptive optics to compensate foraberrations of the human eye are taught in J. Liang, D. Williams and D.Miller, “Supernormal Vision and High-Resolution Retinal Imaging ThroughAdaptive Optics,” J. Opt. Soc. Am. A, Vol. 14, No. 11, pp. 2884-2891,1997 and F. Vargas-Martin, P. Prieto, and P. Artal, “Correction of theAberrations in the Human Eye with a Liquid-Crystal Spatial LightModulator: Limits to Performance,” J. Opt. Soc. Am. A, Vol. 15, No. 9,pp. 2552-2561, 1998. Additionally, J. Liang, B. Grimm, S. Goelz, and J.Bille, “Objective Measurement of Wave Aberrations of the Human Eye withthe Use of a Hartmann-Shack Wave-Front Sensor,” J. Opt. Soc. Am. A, Vol.11, No. 7, pp. 1949-1957, 1994 teaches such a use of adaptive optics.

Furthermore, it is known in the art to use a PSPGD optimizationalgorithm in different applications. For example, see M. Vorontsov, andV. Sivokon, “Stochastic Parallel-Gradient-Descent Technique forHigh-Resolution Wave-Front Phase-Distortion Correction,” J. Opt. Soc.Am. A, Vol. 15, No. 10, pp. 2745-2758, 1998. Also see M. Vorontsov, G.Carhart, and J. Ricklin, “Adaptive Phase-Distortion Correction Based onParallel Gradient-Descent Optimization,” Optics Letters, Vol. 22, No.12, pp. 907-909, 1997.

It is well known in the art to scan an iris and obtain an iris biometricimage. See, for example, U.S. Pat. Nos. 4,641,349, 5,291,560, 5,359,669,5,719,950, 6,289,113, 6,377,699, 6,526,160, 6,532,298, 6,539,100,6,542,624, 6,546,121, 6,549,118, 6,556,699, 6,594,377, 6,614,919, andU.S. Patent Application Nos. 20010026632A1, 20020080256A 1,20030095689A1, 20030120934A1, 20020057438A1, 20020132663A1,20030018522A1, 20020158750A1. However, such images were often notoptimal and their applicability was somewhat limited.

2. Description of Related Art

All references cited herein are incorporated herein by reference intheir entireties.

BRIEF SUMMARY OF THE INVENTION

The invention includes a method for clarifying an optical/digital imageof an object to perform a procedure on an object having the steps ofapplying to the object a light beam formed of incoherent light andreflecting the applied incoherent light beam from the object to providea reflected light beam and providing electrical signals representativeof the reflected light beam. An image quality metric is determined inaccordance with the electrical signals and an image is determined inaccordance with the image quality metric. The procedure is performed inaccordance with the image quality metric.

In a further method of the invention a procedure is performed on an eyehaving an iris. An iris biometric image representative of the iris isobtained and the procedure is performed on an eye in accordance with theiris biometric image.

Additionally a method for optimizing electromagnetic energy in a systemfor processing an image of an object in order to perform a procedure onan object is provided. The method includes applying to the object aplurality of light beams formed of incoherent light at a plurality ofdiffering frequencies and reflecting the plurality of applied incoherentlight beams from the object to provide a plurality of reflected lightbeams. The method also includes providing a corresponding plurality ofelectrical signals representative of the reflected light beams of theplurality of reflected light beams and determining a correspondingplurality of image quality metrics in accordance with the plurality ofelectrical signals. A corresponding plurality of images is determined inaccordance with the plurality of image quality metrics and an image ofthe plurality of images is selected in accordance with a predeterminedimage criterion to provide a selected image. The method also includesdetermining a frequency of the plurality of differing frequencies inaccordance with the selected image to provide a determined frequency andperforming the procedure on an object in accordance with the determinedfrequency.

The inventions also deals with new methods of high-resolution imagingand construction of images of the retina, and adaptive correction anddiagnostics of eye optical aberrations, as well as such imaging ofarticles of manufacture, identifying articles and controlling amanufacturing process. Additionally, the method is applicable toidentifying individuals in accordance with such images for medicalpurposes and for security purposes, such as a verification of anidentity of an individual. These applications can be performed usingadaptive optics techniques based on parallel stochastic perturbativegradient descent (PSPGD) optimization. This method of optimization isalso known as simultaneous perturbation stochastic approximation (SPSA)optimization. Compensation of optical aberrations of the eye andimprovement of retina image resolution can be accomplished using anelectronically controlled phase spatial light modulator (SLM) as awavefront aberration correction interfaced with an imaging sensor and afeedback controller that implements the PSPGD control algorithm.

Examples of the electronically-controlled phase SLMs include a pixelizedliquid-crystal device, micro mechanical mirror array, and deformable,piston or tip-tilt mirrors. Wavefront sensing can be performed at theSLM and the wavefront aberration compensation is performed using retinaimage data obtained with an imaging camera (CCD, CMOS etc.) or with aspecially designed very large scale integration imaging chip (VLSIimager). The retina imaging data are processed to obtain a signalcharacterizing the quality of the retinal image (image quality metric)used to control the wavefront correction and compensate the eyeaberrations.

The image quality computation can be performed externally using animaging sensor connected with a computer or internally directly on animaging chip. The image quality metric signal is used as an input signalfor the feedback controller. The controller computes control voltagesapplied to the wavefront aberration correction. The controller can beimplemented as a computer module, a field programmable gate array (FPGA)or a VLSI micro-electronic system performing computations required foroptimization of image quality metrics based on the PSPGD algorithm.

The use of the PSPGD optimization technique for adaptive compensation ofeye aberration provides considerable performance improvement if comparedwith the existing techniques for retina imaging and eye aberrationcompensation and diagnostics, and therapeutic applications. The firstadvantage is that the PSPGD algorithm does not require the use of laserillumination of the retina and consequently significantly reduces therisk of retina damage caused by a focused coherent laser beam. A furtheradvantage is that the PSPGD algorithm does not require the use of awavefront sensor or wavefront aberration reconstruction computation.This makes the entire system low-cost and compact if compared with theexisting adaptive optics systems for retina imaging. Additionally, thePSPGD algorithm can be implemented using a parallel analog, mix-modeanalog-digital or parallel digital controller because of its parallelnature. This significantly speeds up the operations of the PSPGDalgorithm, providing continuous retina image improvement, eye aberrationcompensation and diagnostics.

Thus, in the adaptive correction technique of the present inventionneither laser illumination nor wavefront sensing are required. Opticalaberration correction is based on direct optimization of the quality ofan retina image obtained using a white light, incoherent, partiallycoherent imaging system. The novel imaging system includes amulti-electrode phase spatial light modulator, or an adaptive mirrorcontrolled with a computer or with a specially designed FPGA or VLSIsystem. The calculated image quality metric is optimized using aparallel stochastic gradient descent algorithm. The adaptive opticalsystem is used in order to compensate severe optical aberrations of theeye and thus provide a high-resolution image and/or of the retina tissueand the eye aberration diagnostic.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The invention will be described in conjunction with the followingdrawings in which like reference numerals designate like elements andwherein:

FIGS. 1A,B show a schematic representation of system suitable forpracticing the eye aberration correcting method of the presentinvention.

FIG. 2 shows a flow chart representation of control algorithm suitablefor use in the system of FIG. 1 when practicing the method of thepresent invention.

FIGS. 3A,B show images of an artificial retina before and aftercorrection of an aberration

FIGS. 4A,B show an eye and a biometric image of the iris of the eye.

FIG. 5 shows a block diagram representation of an iris biometric imagecomparison system which can be used with the aberration correctingsystem of FIG. 1.

FIG. 6 shows a block diagram representation of an iris positioningsystem which can be used in cooperation with the aberration correctingsystem of FIG. 1.

FIG. 7 shows an illumination frequency optimization system which can beused in cooperation with the aberration correcting system of FIG. 1.

FIG. 8 shows an image superpositioning system which can be used with theaberration correcting system of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1A,B there are shown schematic representations ofthe aberration correcting system 10 of the present invention. In theaberration correcting system 10 a light beam from a white light source 1is redirected by a mirror 2 in order to cause it to enter an eye. Inaccordance with the present invention the white light beam from thelight source 1 can be any kind of incoherent light.

The light from the mirror 2 reaches the retina 4 of the eye andreflected light exits the eye to provide two light beams, one passing ineach direction, as indicated by arrow 3. The exiting light beam thenpasses through an SLM 5. The light beam from the SLM 5 enters an imagesensor 6. The image sensor 6 can be a charge coupled capacitor device orany other device capable of sensing and digitizing the light beam fromthe SLM 5.

The imaging sensor 6 can include an imaging chip for performing thecalculations required to determine an image quality metric. The imagequality metric can thus be computed on the imaging chip directly or itcan be calculated using a separate computational device/computer 7 thatcalculates the image quality metric of the retina image. It is the useof a digitized image in this manner that permits the use of anincoherent light rather than a coherent light for performing theoperations of the aberration correction correcting system 10.

The computational device 7 sends a measurement signal representative ofthe image quality metric to a controller 8. The controller 8 implementsa PSPGD algorithm by computing control voltages and applying thecomputed control voltages to the SLM 5. The PSPGD algorithm used by thecontroller 8 can be any conventional PSPGD algorithm known to those ofordinary skill in the art. In the preferred embodiment of the invention,the controller 8 continuously receives digital information about thequality of the image and continuously updates the control voltagesapplied to the SLM 5 until the quality of the retina image is optimizedaccording to predetermined image quality optimization criteria.

Referring now to FIGS. 2 and 3A,B there are shown a flow chartrepresentation of a portion of a PSPGD control algorithm 20 for use incooperation with the aberration correcting system 10 in order topractice the present invention as well as representations of thecorrected image, both before correction (3A) and after correction (3B).In order to simplify the drawing a single iterative step of the PSPGDcontrol algorithm 20 is shown with a loop for repeating the singleiterative step until the quality of the compensation is acceptable.

In step 25 of the PSPGD control algorithm 20 a measurement andcalculation of the image quality metric is performed. This step includesthe retinal image capture performed by the sensor 5 and the calculationof the image quality metric performed by the computational device 7within the aberration correcting system 10. The image captured by thesensor 5 at the beginning of the operation of the PSPGD controlalgorithm 20 can be substantially as shown in FIG. 3A, as previouslydescribed. One can use any relevant metric entity as an image qualitymetric. For example, in one embodiment of the PSPGD control algorithm 20the image quality metric can be a sharpness function. A sharpnessfunction suitable for use in the present invention can be defined as

J=∫|∇ ² I(x,y)|dxdy

where I(x,y) is the intensity distribution in the image, and ∇² is theLaplacian operator over the image. The Laplacian can be calculated byconvolving the image with a Laplacian kernel. The convolving of theimage can be performed by a special purpose VLSI microchip. Alternately,the convolving of the image can be performed using a computer thatreceives an image from a digital camera as described in more detailbelow. In another embodiment different digital high-pass filters can beused rather than the Laplacian operator.

Additionally, a frequency distribution function can be used rather thana sharpness function when determining the image quality metric. The useof a frequency distribution function allows the system to distinguishtissues of different colors. This is useful where different kinds oftissue, for example, different tumors, have different colors. Locatingtumors in this manner also permits the invention to provide tumorlocation information, such as a grid location on a grid having apre-determined reference in order to assist in diagnosis and surgery. Italso permits the invention to provide tumor size and type information.Additionally, the use of a frequency distribution function permits asurgeon to determine which light frequencies are best for performingdiagnosis and surgery.

The image quality metric J can also be calculated either optically ordigitally using the expression introduced in:

J=∫|F{exp[ iγI(x,y)]}|⁴ dxdy

Where F is the Fourier transform operator and γ is a parameter that isdependent upon the dynamic range of the used image.

In step 30 of the PSPGD control algorithm 20 random perturbations in thevoltages applied to the SLM 5 electrodes are generated. The SLM 5 can bea liquid crystal membrane for modifying the light beam according to theelectrical signals from controller 8 in a manner well understood bythose skilled in the art.

In order to generate the perturbations for application to the electrodesfor the SLM 5 random numbers with any statistical properties can be usedas perturbations. For example, uncorrelated random coin flipperturbations having identical amplitudes |u_(j) and the Bernoulliprobability distribution:

du _(j) =±p, Pr(du _(j) =+p)=0.5

for all j=1, N(N=the number of control channels) and iteration numberscan be used. Note that Non-Bernoulli perturbations are also allowed inthe PSPGD control algorithm 20.

In step 35 of the PSPGD control algorithm 20 a measurement of theperturbed image quality metric and a computation of the image qualityperturbation δJ^((m)) are performed. Following the determination of theperturbed image quality metric, the gradient estimations

{tilde over (J)}′ _(j) ^((m)) =δJ ^((m))π_(j) ^((m))

are computed as shown in step 40.

The updated control voltages are then determined as shown in step 45.Therefore, a calculation of:

u _(j) ^((m+1)) =u _(j) ^((m)) −γδJ ^((m))π_(j) ^((m))

is performed.

To further improve the accuracy of gradient estimation in the PSPGDcontrol algorithm 20 a two-sided perturbation can be used. In atwo-sided perturbation two measurements of the cost functionperturbations J⁺ and J⁻ are taken. The two measurements correspond tosequentially applied differential perturbations +u_(j)/2 and −u_(j)/2.

It follows that:

dJ=dJ ⁺ −dJ ⁻ and

{tilde over (J)}′ _(j) =δJδu _(j)

which can produce a more accurate gradient estimate.

The process steps 25-45 of the PSPGD control algorithm 20 are repeatedinteractively until the image quality metric has reached an acceptablelevel as determined in step 50. The choice of an acceptable level of theimage quality metric is a conventional one well known to those skilledin the art. As shown in step 55 the aberration is then corrected and animage of the retina can be taken. The image resulting from the operationof the PSPGD algorithm 20 can be as shown in FIG. 3B.

The eye aberration function (x,y) can be calculated from known voltagesapplied to wavefront correction {u_(j)} at the end of the iterativeoptimization process and known response functions of {S_(j)(x,y)}wavefront correction.

${j\left( {x,y} \right)} = {\sum\limits_{j = 1}^{N}\; {u_{j}{{S_{j}\left( {x,y} \right)}.}}}$

Referring now to FIGS. 4A,B, there is shown an eye 80 having an iris 84with a pupil 88 therein and an iris biometric image 90. The irisbiometric image 90 is a biometric image of the iris 84, which can beobtained using an iris scanning system, such as the aberrationcorrecting system 10. In an alternate embodiment of the invention, theiris biometric image 90 can be obtained by any other system (not shown)capable of scanning and digitizing an iris and providing an image thatis characteristic of the iris, such as a bar code type output as shownin FIG. 4B. Furthermore, it will be understood that every human eye hasan unique iris biometric image when it is scanned and digitized in thismanner. Thus, an iris biometric image can be used as a unique identifierof an individual in the manner that fingerprints are used or even todistinguish between the left and right eyes of an individual.

When the predetermined image quality is obtained, a plurality oflocations 92 within the iris 84 can be defined. In one preferredembodiment of the invention, four locations 92 can be selected. The fourlocations 92 can be disposed on the corners of a rectangle which isconcentric with the iris 84. The locations 92 can thus be easily used tofind the center of the iris 84. The four locations 92 are represented onthe iris biometric image 90 in accordance with the mathematicalrelationships previously described. Thus, the xy coordinates of thelocations 92 may be mapped into corresponding xy coordinates within theiris biometric image 90 if a spatial transform such as the sharpnessfunction is used, while they may be convolved over areas of the irisbiometric image 90 if a frequency or other transform is used.

Various features already occurring in the eye 80 also have correspondingrepresentations within the iris biometric image 90. The location andstudy of such features can be used to diagnose pathologies, for example,to diagnose tumors and to determine the position of the eye iris 84. Asa further example, a feature can be studied several times over a periodof time to determine how its parameters are is changing.

Referring now to FIG. 5, there is shown the iris biometric imagecomparison system 100. The iris biometric image comparison system 100receives the previously determined iris biometric image 90 as one of itsinputs. Additionally, a new iris biometric image 95 is produced, forexample, before or during the performance of a procedure on the eye 80.The new iris biometric image 95 is received by the image comparisonsystem 100 as a second input. The new iris biometric image 95 can beprovided by the aberration correction system 10. The light beam used toobtain the iris biometric image 95 can be the same light beam being usedfor other purposes during the procedure.

When using the aberration correcting system 10, the image can beoptimized by executing additional iterations of the PSPGD controlalgorithm 20. The algorithm can be iterated until a predetermined imagequality is obtained and computing the image quality metric within thecomputer 7 as previously described. In addition to performing moreiterations of the PSPGD control algorithm 20, increased imagesensitivity quality can be obtained by increasing the number of pixelsin the digitized image or increase image sensitivity can be obtained byincreasing the number of measuring points in the iris 84.

When performing the method of the image comparison system 100 the irisbiometric image 90 can be assumed by the image comparison system 100 tobe the correct iris biometric image of the iris 84 upon which theprocedure is to be performed. Furthermore, it can be assumed that theiris biometric image 90 applied to the image comparison system 100 wasobtained when the position and orientation of the eye 80 were correct.

The iris biometric images 90, 95 are compared by the image comparisonsystem 100 at decision 104. A determination is made as to whether theiris biometric image 95 is an image of the same iris 84 that was imagedto produce the enrolled iris biometric image 90. Any of the well knowncorrelation techniques can be used for the comparison. Substantiallysimilar correlation techniques can be used for the comparison if thelocations 92 are used or if other markings within the iris 84 are used.The sensitivity of the comparison can be adjusted by those skilled inthe art.

If the determination of decision 104 is negative, then the procedurebeing performed on the eye 80 is not continued as shown in block 102. Ifthe determination of decision 104 is positive, then a determination canbe made in decision 106 whether the iris 84 is positioned in the xydirections correctly and oriented or rotated correctly at the time thatthe iris biometric image 95 was produced. The determination of decision106 can be used for a number of purposed. For example, it could be usedto direct a beam of light to a predetermined location within the eye 80.Thus, if the determination of decision 106 is negative, the beam can beredirected as shown in block 110. The position of the iris 84 can bechecked again in decision 106. When the position of the iris 84 iscorrect, the procedure can begin, as shown in block 112.

The determination of decision 106 can be made in accordance with therepresentations of locations 92 within the iris 84 selected when irisbiometric image 90 was obtained. If corresponding locations are found inthe iris biometric image 95 in the same positions, the determination ofdecision 106 is positive. Alternately, the determination of decision 106can be made in accordance with predetermined features or markings withinthe iris 84 other than the locations 92. The method of the imagecomparison system 100 can be used to determine whether the iris 84 isrotated or translated in the direction of either of the axes orthogonalto the arrow 3 shown in FIGS. 1A,B.

Referring now to FIG. 6, there is shown the iris positioning system 120.The iris positioning system 120 is adapted to precisely position theiris 84 while performing a procedure on the eye 80. The iris positioningsystem 120 differs from the iris biometric image comparison system 100primarily in the fact that the iris positioning system 120 is providedwith a servo 124. The servo 124 is effective in modifying the relativepositions of the iris 84 and the camera 6 of the aberration correctingsystem 10 which can be coupled to equipment (not shown) used to performthe procedure in the eye.

In the iris positioning system 120 a determination is made in decision104 whether the iris biometric images 90, 95 were made on the same eyeas previously described with respect to image comparison system 100. Theprocedure is continued only if a positive determination is made. Adetermination is then made in decision 106 whether the iris 84 is in thecorrect position. The determination of decision 106 can be made bycomparing the iris biometric images 90, 95 in accordance with thelocations 92 or any other markings within the iris 84 as previouslydescribed. The determination made can be, for example, whether the iris84 is rotated or translated in the x or y direction at the time that theiris biometric image 95 is obtained.

When a determination is made that the iris 84 is in an incorrectposition, a correction signal representative of the error is calculated.The error correction signal is applied to the servo 124. The servo 124is adapted to receive the error correction signal resulting from thedeterminations of decision 106 and to adjust the relative positions ofthe iris 84 and the equipment performing the procedure in accordancewith the signal in a manner well understood by those skilled in the art.Servos 124 capable of applying both rotational and multi-axistranslational corrections are both provided in the preferred embodimentof the invention. Either the object such as the iris 84 or the equipmentcan be moved in response to the determination of decision 106.

The method of the iris positioning system 120 can be repeatedlyperformed, or constantly performed, during the performance of aprocedure on the eye 80 to re-capture, re-evaluate or refine the processthe eye 80. Thus, the relative positions of the iris 84 and theprocedure equipment can be kept correct at all times.

Referring now to FIG. 7, there is shown the illumination frequencyoptimization system 130. The illumination frequency optimization system130 is an alternate embodiment of the aberration correcting system 10.Within the frequency optimization system 130 a variable frequency lightsource 132 rather than a single frequency light source applies a lightbeam to the eye 80. The variable frequency light source 132 can be atunable laser, a diode, filters in front of a light source, adiffraction grating or any other source of a plurality of frequencies oflight. An image quality metric can be obtained and optimized in themanner previously described with respect to system 10.

Using the variable frequency light source 132, it is possible toconveniently adjust the frequency of the light beam used to illuminatethe eye 80 or object 80 at a plurality of differing frequencies and toobtain a plurality of corresponding image quality metrics. In order todo this, the frequency of the light applied to the eye 80 by thevariable frequency light source 132 can be repeatedly adjusted and a newimage quality metric can be obtained at each frequency. Each imagequality metric obtained in this manner can be optimized to apredetermined level. The levels of optimization can be equal or they candiffer. While the optimizations should be done using the frequencydistribution, it is possible to return to images optimized using thefrequency distribution and sharpen using the sharpness function.

It is well understood that differing types of tissue can be visualizedbest with differing frequencies of light. For example, tumors, lesions,blood and various tissues as well as tissues of varying pathologies canbe optimally visualized at different frequencies since their absorptionand reflection properties vary. Thus, by adjusting the frequency appliedto the eye 80 by the variable frequency light source 132 and viewing theresults, the best light for visualizing selected features can bedetermined. Furthermore, using this method there can be severaloptimized images for one eye. For example, there can be differentoptimized images, for a tumor, for a lesion and for blood. Thedetermination of the best frequency for each image can be a subjectivejudgment made by a skilled practitioner.

A skilled practitioner can use the illumination frequency optimizationsystem 130 to emphasize and de-emphasize selected features within imagesof the eye 80. For example, when obtaining an iris biometric image 95,the iris 84 may be clouded due to inflammation of the eye 80 or thepresence of blood in the eye 80. It is possible to effectively removethe effects of the inflammation blood with the assistance of thefrequency optimization system 130 by varying the frequency of the lightprovided by the light source 132 until the optimum frequency is foundfor de-emphasizing the inflammation or blood and permitting the obscuredfeatures to be seen. In general, it is often possible to visualizefeatures when another feature is superimposed on them by removing thesuperimposed feature using system 130.

In order to remove the effects of the inflammation or blood, a pluralityof images of the eye 80 can be provided and the frequency at which theblood or inflammation is least apparent can be determined. Removingthese features from the iris biometric image 95 can facilitate itscomparison with the iris biometric image 90. Furthermore, when thebiometric image 95 is obtained from the iris 110 of a person wearingsunglasses, it is possible to remove the effects of the sunglasses inthe same manner and identify an eye 80 behind the sunglasses. Thisfeature is useful when identifying people outside of laboratoryconditions.

Referring now to FIG. 8, there is shown the image superposition system150. In many cases it is desirable to perform a procedure on an eye 80when selected features of the eye 80 are obscured by other features,where different features are visualized best at different frequencies,or where the criteria for emphasizing and de-emphasizing features canchange during a procedure. Image superposition 100 can be used to obtainimproved feature visualization under these and other circumstances.

For example, white light is often preferred for illuminating an iris 84because in many cases white light shows the most features. However, ifwhite light is used to illuminate an iris 84 when the iris 84 is cloudedwith blood, the blood can block the white light. This can make itdifficult, or even impossible, to visualize the features that areobscured by the blood. One solution to this problem is to use red lightto illuminate the iris 84 and visualizes the features obscured by theblood.

However, the red light could fail to optimally visualize the featureswhich are normally visualized best using, for example, white light. Theimage superposition system 150 can solve this problem by superimposingtwo images such as the direct image 166 and the projected image 170,where the images 166, 170 are obtained using light sources of differingfrequencies. The optimum frequencies for obtaining each of the images166, 170 can be determined using the illumination frequency optimizationsystem 130.

For example, an object 168 to be visualized can be illuminated withincoherent white light to provide the direct image 166. Illumination ofthe object 168 by white light to produce the direct image 166 can beprovided using any of the known methods for providing such illuminationof objects to provide digital images. The direct image 166 can be sensedand digitized using an image sensor 152 which senses light travelingfrom the object 168 in the direction indicated by the arrows 156, 164.

The image sensor 152 senses the direct image 166 of the object 168 byway of a superposition screen 160. The superposition screen 160 can beformed of any material capable of transmitting a portion to the lightapplied to it from the object 168 to the image sensor 152, andreflecting a portion of the same light. For example, the superpositionscreen 168 can be formed of glass or plastic. A viewer, a TV screen or agradient filter can also serve as the superposition screen 160. Thescreen 160 can also be a gradient filter. In a preferred embodiment ofthe invention, the angle 172 of the superposition screen 160 can beadjusted to control the amount of light it transmits and the amount itreflects.

The projected image 170 of the object 168 can be obtained using, forexample, the aberration correcting system 10 as previously described.Illumination with red light or any other frequency of light can be usedwithin the aberration correcting system 10 to obtain the superpositionimage 178. The superposition image 178 is applied to an image projector176 by the aberration correcting system 10. The image projector 176transmits the projected image 170 in accordance with the superpositionimage 178 in the direction indicated by the arrow 174 and applies it tothe superposition screen 160.

A portion of the projected image 170 applied to the superposition screen160 by the projector 176 is reflected off of the superposition screen160 and applied to the image sensor 152 in the direction indicated bythe arrow 156. The amount of the projected image 170 reflected to theimage sensor 152 can be adjusted by adjusting the angle 172 of thesuperposition screen 160. The image projector 176 is disposed in alocation adapted to apply the projected image 170 to the superpositionscreen 160 in the same region of the superposition screen 160 where thedirect image 166 is applied. When the images 166, 170 are applied to thesuperposition screen 160 in this manner, they are superimposed and theimage sensed by the image sensor 152 is thus the superposition orcomposite of the images 166, 170.

Adjustment of the angle 172 results in emphasizing and de-emphasizingthe images 166, 170 relative to each other. This is useful, for example,where different features visualized selectively at differing frequenciesmust be brought in and out of visualization in the composite image fordifferent purposes. Another time where this is useful is when theintensity of one of the images 166, 170 is too high relative to theother and must be adjusted down or too low and must be adjusted up.

In various alternate embodiments of the image superposition system 150,either or both of the images 166, 170 can be optimized using the PSPGDalgorithm 20 within the aberration correction system 10. Furthermore,the images 166, 170 can be optimized to differing degrees by the PSPGDalgorithm 20 and with differing optimization criteria in order toemphasis one over the other or to selectively visualize selectedfeatures within the images 166, 170 and thus, within the composite imagesensed by image sensor 152. This permits selected features of the eye 80to be brought into view and brought out of view as convenient atdifferent times during a diagnosis or a procedure.

Thus, the illumination used to obtain the images 166, 170 superimposedby the image superposition system 150 does not need to be red and whitelight. The illumination used can be light of any differing frequencies.The frequencies selected for obtaining the images 166, 170 can beselected in accordance with the sharpness function on the frequencydistribution as previously described.

The images superimposed by the image superposition system 150 do notneed to be obtained by way of a camera, such as the camera 6 of theaberration correction system 10. A microscope, an endoscope, or anyother type of device having an image sensor capable of capturingtransmission, absorption or reflection properties of an object or tissuein a normal state or enhancement by such materials as markers andchromophores and thereby providing an optical/digital signal that can beapplied to the computer 7 for optimization using the PSPGD algorithm 20can be used. Thus, for example, an image obtained from an endoscope or amicroscope can be superimposed upon an image obtained from an camerausing the method of the present invention. Images from endoscopes,microscopes and other devices can be digitized, and superimposed andsynthesized with each other. It will be understood that images obtainedfrom such devices and optimized using the PSPGD algorithm 20 can be usedin any other way that images obtained from the PSPGD algorithm 20 usingcamera 6 are used.

The description herein will so fully illustrate my invention that othersmay, by applying current or future knowledge, adopt the same for useunder various conditions of service. For example, the invention may beused for ophthalmological procedures such as photocoagulation, opticalbiopsies such as measuring tumors anywhere in the eye, providingtherapy, performing surgery, diagnosis or measurements. Additionally, itcan be used for performing procedures on eyes outside of laboratory ormedical environments. Furthermore, the method of the present inventioncan be applied to any other objects capable of being imaged in additionto eyes and images of an object provided. In accordance with the methodof the invention can be used when performing such procedures on otherobjects.

While the invention has been described in detail and with reference tospecific examples thereof, it will be apparent to one skilled in the artthat various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

1. A device comprising: (a) an optional electromagnetic energy source;and (b) a sensor for capturing imagewise electromagnetic energy from anobject, wherein said imagewise electromagnetic energy is receivedthrough a: spatial energy modulator in communication with (ii) acontroller comprising a parallel stochastic perturbation gradientdescent or a simultaneous perturbation stochastic approximationoptimization algorithm.
 2. The device of claim 1, wherein said spatialenergy modulator is a pixelized liquid crystal device, a micromechanicalmirror array, a piston mirror, a tip-tilt mirror or a deformable mirror.3. The device of claim 1, wherein said sensor is a CCD camera, a CMOScamera or a very large scale integration imaging device.
 4. The deviceof claim 1, wherein said controller comprises a parallel controller. 5.The device of claim 1, further comprising an integral device forexecuting said algorithm computations.
 6. The device of claim 1, whereinsaid energy source is a variable frequency source.
 7. The device ofclaim 1, wherein said energy source produces incoherent light.